Accumulation of intermediate density lipoprotein in plasma after intravenous administration of hepatic triglyceride lipase antibody in rats.

In an attempt to define the role of hepatic triglyceride lipase in plasma lipoprotein metabolism, in vivo experiments using an antibody specifically prepared against this enzyme were conducted in rats. The antibody gamma globulins were injected into rats three times during a 40 min period. Control rats received non-immune rabbit gamma globulins prepared in the same way as the immune gamma globulins. After treatment, blood was taken and the plasma was separated. Plasma lipoproteins were fractionated by ultracentrifugation into VLDL, IDL, LDL and HDL. Treatment of recipient rats with the antibody significantly increased cholesterol, phospholipid and protein concentrations in the IDL fraction. These concentrations were also elevated in the LDL fraction. However, we speculate that this increase represents the accumulation of small remnants rather than bona fide LDL. VLDL compositions in antibody-treated rats did not differ from those in control animals. In HDL, only the phospholipid level was elevated in antibody-treated rats. The data of the present study indicate that hepatic triglyceride lipase mediates the catabolism of remnant lipoproteins by the liver.